Between 1.5 and 2 million Americans sustain a traumatic brain injury (TBI) each year (Anonymous, “Traumatic Brain Injury,” Center for Disease Control and Prevention, National Center for Injury Prevention and Control, 2003, Vol. 2003). In the U.S. it is estimated that TBI is responsible for 50,000 deaths and 100,000 hospitalizations annually (Anonymous, “Traumatic Brain Injury,” Center for Disease Control and Prevention, National Center for Injury Prevention and Control, 2003, Vol. 2003). Over 80,000 are disabled annually, approximately 17,000 of whom require specialized care for life (Kraus (1997) “Epidemiology of Head Injury,” in Head Injury, ed. Cooper (Williams & Wilkins Co., Baltimore) pp 1-19; Selecki et al. (1982) Australian & New Zealand Journal of Surgery 52(1):93-102). In addition to the initial lesion created by abrupt trauma to the brain, excessive biomechanical force initiates a cascade of secondary deleterious events that can dramatically increase lesion size, morbidity, and mortality for days to months after the initial injury (McIntosh et al. (1996) Lab Invest, 74(2):315-42; Stambrook et al. (1990) Can J Surg 33(2):115-8). Despite the enormity of the problem, an effective pharmacological treatment for TBI in humans has not been identified.
Continuous intravenous (IV) infusion allows rapid drug delivery and achievement of a continuous steady state serum concentration, but this route for administration of progesterone is not FDA approved in the United States. Only three human studies involving the use of IV progesterone in the US have been reported. In an FDA-approved (IND 33,580) phase I clinical trial, Christen, et al. administered IV progesterone dissolved in an ethanol-Intralipid 20% fat emulsion combined with doxorubicin over 24 hours to 32 cancer patients without toxic effects (Christen et al. (1993) Journal of Clinical Oncology 11(12):2417-2426). In a second study, Allolio et al. reported that steady state serum concentrations (CSS) of progesterone could be achieved in healthy male volunteers (Allolio et al. (1995) European Journal of Endocrinology 133(6):696-700). The third study was modeled after the study performed by Christen et al, but was a phase II trial testing the effect of coadministration of high-dose progesterone on the pharmacokinetics of paclitaxel. The manuscript did not present detailed information on the pharmacokinetics of progesterone.
Following a traumatic injury to the central nervous system, a cascade of physiological events leads to neuronal loss including, for example, an inflammatory immune response and excitotoxicity resulting from the initial impact disrupting the glutamate, acetylcholine, cholinergic, GABAA, and NMDA receptor systems. In addition, the traumatic CNS injury is frequently followed by brain and/or spinal cord edema that enhances the cascade of injury and leads to further secondary cell death and increased patient mortality. Methods are needed for the in vivo treatment of traumatic CNS injuries that are successful at providing subsequent trophic support to remaining central nervous system tissue, and thus enhancing functional repair and recovery, under the complex physiological cascade of events which follow the initial insult.